In one type of offshore drilling, a subsea wellhead will be installed at the sea floor. A riser will connect to the wellhead and extend upward to a drilling vessel floating at the surface. A blowout preventer stack, hereinafter referred to as a BOP, will be located within the riser.
It is a good practice to test a BOP by closing the BOP on drill pipe and applying pressure below the drill pipe. In addition, it is a good practice to test full closure of the BOP with the drill pipe pulled above the BOP. These operations also test the seal of the wellhead connector to the subsea wellhead housing. While test tools are available, improvements are desired.